Spanning's REST API call limit
When first installed, Spanning is limited to 15% of your total available Salesforce REST API calls per day by default. This is to ensure that Spanning Backup does not exhaust the API call limit for your instance. You can increase or decrease this API call limit at any time from your Spanning Dashboard.
Spanning can back up between 200-1,000 records in your account per API call (depending on how many fields are in each record). However, we can back up only one attachment per API call. We recommend editing the Spanning API call limit accordingly. This way, Spanning can back up all of the data in your account in a timely manner without exhausting all of the API calls in your Salesforce instance.
It is important to remember that the initial backup of your Salesforce data takes the longest to complete since we are backing up all of the data in your account. After the initial backup is completed, subsequent daily backups will be much faster since we will only be backing up new and changed data.
Please note that if the Spanning API limit is set too low, backups may run for many days if the API limit is reached before the backups complete. You can always modify the number of API calls that Spanning uses. After your initial backup completes, you can recalibrate this number to not use as many API calls.
See these topics for more on working with Spanning's REST API call limit:

To determine the correct number of API calls for your instance, first check the number of available API calls in your Salesforce instance. Next, determine how many total attachments are in your instance by following these steps:
- Log in to your Salesforce account as the admin user.
- Click the Setup button in the upper-right corner of the screen.
- Click the Data Management button in the left-panel navigation pane (if you are on Salesforce Lightning Experience, click the Data button in the left panel navigation pane).
- Select the Storage Usage option from the sub menu.
- Under the Current File Storage Usage subheading, you see the number of attachments:
- If needed, modify the number of API calls as described in To change the number of API calls that Spanning uses.

Under special circumstances, an environment might be so large or the rate of change so significant that the normal REST API capacity is not enough to keep up. In these rare cases, Spanning can utilize Bulk API methods instead to process large batches of data for backup.
- Bulk queries are metered separately and differently from REST queries.
- Bulk queries are measured and limited by the hour.